Role of 5HT1A Receptors in the Neuroprotective and Behavioral Effects of Cannabidiol in Hypoxic–Ischemic Newborn Piglets

Cannabidiol in experimental cerebral ischemia

The absence of blood flow in cerebral ischemic conditions triggers a multitude of intricate pathophysiological mechanisms, including excitotoxicity, oxidative stress, neuroinflammation, disruption of the blood-brain barrier and white matter disarrangement. Despite numerous experimental studies conducted in preclinical settings, existing treatments for cerebral ischemia (CI), such as mechanical and pharmacological therapies, remain constrained and often entail significant side effects. Therefore, there is an imperative to explore innovative strategies for addressing CI outcomes. Cannabidiol (CBD), the most abundant non-psychotomimetic compound derived from Cannabis sativa, is a pleiotropic substance that interacts with diverse molecular targets and has the potential to influence various pathophysiological processes, thereby contributing to enhanced outcomes in CI. This chapter provides a comprehensive overview of the primary effects of CBD in in vitro and diverse animal models of CI and delves into some of its plausible mechanisms of neuroprotection.

Cannabidiol Anticonvulsant Effects Against Lithium-Pilocarpine-Induced Status Epilepticus in Male Rats Are Mediated by Neuroinflammation Modulation and Cannabinoids 1 (CB1), But Not CB2 and GABAA Receptors

Background: Status epilepticus (SE) is a series of seizures that can lead to serious neurological damages. Cannabidiol (CBD) is extracted from the cannabis plant, which has been approved as an antiseizure medication. This study aimed to determine the efficacy of various doses of CBD on lithium-pilocarpine-induced SE in rats and possible involvement of multiple pharmacological pathways. We hypothesized that cannabinoid receptors type 1 (CB1) and CB2, as well as GABAA receptors, might have important roles in the anticonvulsant effects of CBD against SE by its anti-inflammatory effects. Methods: SE was induced by intraperitoneal (i.p.) injection of lithium (127 mg/kg, i.p.) and pilocarpine (60 mg/kg, i.p., 20 h after lithium). Forty-two male rats were divided into seven groups (including control and sham groups), and the treated groups received different doses of CBD (1, 3, 5, 10, and 25 mg/kg, i.p.). SE score was recorded over the next 2 h following pilocarpine injection. Then, we measured the levels of pro-inflammatory cytokines, including interleukin (IL)-lβ and tumor necrosis factor (TNF)-α, using ELISA kits. Also we analyzed the expression of CB1, CB2, and GABAA receptors using the Western blot technique. Results: CBD at 5 mg/kg significantly reduced Racine's scale and duration of seizures, and increased the onset time of seizure. Moreover, CBD 5 mg/kg caused significant reductions in the elevated levels of IL-lβ and TNF-α, as well as a significant increase in the decreased level of CB1 receptor expression compared to the control group. In other word, CBD reverted the effects of SE in terms of neuroinflammation and CB1 receptor. Based on the obtained results, CBD was not able to restore the declined levels of CB2 or GABAA receptors. Conclusion: Our study found anticonvulsant effects of CBD on the SE rat model induced by lithium-pilocarpine with probable involvement of CB1 receptors and anti-inflammatory effects by reducing IL-1β and TNF-α markers independent of CB2 and GABAA receptors.

Allosteric Modulators of Serotonin Receptors: A Medicinal Chemistry Survey

Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter regulating numerous physiological functions, and its dysregulation is a crucial component of the pathological processes of schizophrenia, depression, migraines, and obesity. 5-HT interacts with 14 different receptors, of which 5-HT1A-1FRs, 5-HT2A-CRs, and 5-HT4-7Rs are G protein-coupled receptors (GPCRs), while 5-HT3R is a ligand-gated ion channel. Over the years, selective orthosteric ligands have been identified for almost all serotonin receptors, yielding several clinically relevant drugs. However, the high degree of homology between 5-HTRs and other GPCRs means that orthosteric ligands can have severe side effects. Thus, there has recently been increased interest in developing safer ligands of GPCRs, which bind to less conserved, more specific sites, distinct from that of the receptor's natural ligand. The present review describes the identification of allosteric ligands of serotonin receptors, which are largely natural compounds (oleamide, cannabidiol, THC, and aporphine alkaloids), complemented by synthetic modulators developed in large part for the 5-HT2C receptor. The latter are positive allosteric modulators sought after for their potential as drugs preferable over the orthosteric agonists as antiobesity agents for their potentially safer profile. When available, details on the interactions between the ligand and allosteric binding site will be provided. An outlook on future research in the field will also be provided.

Cannabidiol Exerts Sedative and Hypnotic Effects in Normal and Insomnia Model Mice Through Activation of 5-HT1A Receptor

Cannabis sativa has been used for improving sleep for long history. Cannabidiol (CBD) has drown much attention as a non-addictive psychoactive component in Cannabis sativa extract. However, the effects of CBD on sleep architecture and it's acting mechanism remains unclear. In the present study, we evaluated the sedative-hypnotic effect of cannabidiol (CBD), assessed the effects of CBD on sleep using a wireless physiological telemetry system. We further explored the therapeutic effects of CBD using 4-chloro-dl-phenylalanine (PCPA) induced insomnia model and changes in sleep latency, sleep duration and intestinal flora were evaluated. CBD shortened sleep latency and increases sleep duration in both normal and insomnia mice, and those effects were blocked by 5-HT1A receptor antagonist WAY100635. We determined that CBD increases 5-HT1A receptors expression and 5-HT content in the hypothalamus of PCPA-pretreated mice and affects tryptophan metabolism in the intestinal flora. These results showed that activation of 5-HT1A receptors is one of the potential mechanisms underlying the sedative-hypnotic effect of CBD. This study validated the effects of CBD on sleep and evaluated its potential therapeutic effects on insomnia.

Antagonization of OX1 Receptor Potentiates CB2 Receptor Function in Microglia from APPSw/Ind Mice Model

Microdialysis assays demonstrated a possible role of orexin in the regulation of amyloid beta peptide (Aß) levels in the hippocampal interstitial fluid in the APP transgenic model. CB₂R is overexpressed in activated microglia, showing a neuroprotective effect. These two receptors may interact, forming CB₂-OX₁-Hets and becoming a new target to combat Alzheimer's disease. Aims: Demonstrate the potential role of CB₂-OX₁-Hets expression and function in microglia from animal models of Alzheimer's disease. Receptor heteromer expression was detected by immunocytochemistry, bioluminescence resonance energy transfer (BRET) and proximity ligation assay (PLA) in transfected HEK-293T cells and microglia primary cultures. Quantitation of signal transduction events in a heterologous system and in microglia cells was performed using the AlphaScreen^® SureFire^® kit, western blot, the GCaMP6 calcium sensor and the Lance Ultra cAMP kit (PerkinElmer). The formation of CB₂-OX₁ receptor complexes in transfected HEK-293T cells has been demonstrated. The tetrameric complex is constituted by one CB₂R homodimer, one OX₁R homodimer and two G proteins, a G_i and a G_q. The use of TAT interfering peptides showed that the CB₂-OX₁ receptor complex interface is TM4-TM5. At the functional level it has been observed that the OX₁R antagonist, SB334867, potentiates the action induced by CB₂R agonist JWH133. This effect is observed in transfected HEK-293T cells and microglia, and it is stronger in the Alzheimer's disease (AD) animal model APPSw/Ind where the expression of the complex assessed by the proximity ligation assay indicates an increase in the number of complexes compared to resting microglia. The CB₂-OX₁ receptor complex is overexpressed in microglia from AD animal models where OX₁R antagonists potentiate the neuroprotective actions of CB₂R activation. Taken together, these results point to OX₁R antagonists as drugs with therapeutic potential to combat AD. Data access statement: Raw data will be provided by the corresponding author upon reasonable requirement.